Signaling of inter layer prediction in video bitstream

ABSTRACT

There is included a method and apparatus comprising computer code configured to cause a processor or processors to perform parsing at least one video parameter set comprising at least one syntax element indicating whether at least one layer in the scalable bitstream is one of a dependent layer of the scalable bitstream and an independent layer of the scalable bitstream, determining a number of dependent layers, including the dependent layer, of the scalable bitstream based on a plurality of flags included in the VPS, decoding a picture in the dependent layer by parsing and interpreting an inter-layer reference picture list, and decoding a picture in an independent layer without parsing and interpreting the inter-layer reference picture list.

CROSS REFERENCE TO RELATED APPLICATION

This application is a Continuation of U.S. application Ser. No.17/019,713 filed Sep. 14, 2020, which claims priority to provisionalapplication U.S. 62/903,652 filed on Sep. 20, 2019 which are herebyexpressly incorporated by reference, in their entirety, into the presentapplication.

BACKGROUND 1. Field

The disclosed subject matter relates to video coding and decoding, andmore specifically, to the signaling of inter-layer prediction in videobitstream.

2. Description of Related Art

Video coding and decoding using inter-picture prediction with motioncompensation has been known for decades. Uncompressed digital video canconsist of a series of pictures, each picture having a spatial dimensionof, for example, 1920×1080 luminance samples and associated chrominancesamples. The series of pictures can have a fixed or variable picturerate (informally also known as frame rate), of, for example 60 picturesper second or 60 Hz. Uncompressed video has significant bitraterequirements. For example, 1080p60 4:2:0 video at 8 bit per sample(1920×1080 luminance sample resolution at 60 Hz frame rate) requiresclose to 1.5 Gbit/s bandwidth. An hour of such video requires more than600 GByte of storage space.

One purpose of video coding and decoding can be the reduction ofredundancy in the input video signal, through compression. Compressioncan help reducing aforementioned bandwidth or storage spacerequirements, in some cases by two orders of magnitude or more. Bothlossless and lossy compression, as well as a combination thereof can beemployed. Lossless compression refers to techniques where an exact copyof the original signal can be reconstructed from the compressed originalsignal. When using lossy compression, the reconstructed signal may notbe identical to the original signal, but the distortion between originaland reconstructed signal is small enough to make the reconstructedsignal useful for the intended application. In the case of video, lossycompression is widely employed. The amount of distortion tolerateddepends on the application; for example, users of certain consumerstreaming applications may tolerate higher distortion than users oftelevision contribution applications. The compression ratio achievablecan reflect that: higher allowable/tolerable distortion can yield highercompression ratios.

A video encoder and decoder can utilize techniques from several broadcategories, including, for example, motion compensation, transform,quantization, and entropy coding, some of which will be introducedbelow.

Historically, video encoders and decoders tended to operate on a givenpicture size that was, in most cases, defined and stayed constant for acoded video sequence (CVS), Group of Pictures (GOP), or a similarmulti-picture timeframe. For example, in MPEG-2, system designs areknown to change the horizontal resolution (and, thereby, the picturesize) dependent on factors such as activity of the scene, but only at Ipictures, hence typically for a GOP. The resampling of referencepictures for use of different resolutions within a CVS is known, forexample, from ITU-T Rec. H.263 Annex P. However, here the picture sizedoes not change, only the reference pictures are being resampled,resulting potentially in only parts of the picture canvas being used (incase of downsampling), or only parts of the scene being captured (incase of upsampling). Further, H.263 Annex Q allows the resampling of anindividual macroblock by a factor of two (in each dimension), upward ordownward. Again, the picture size remains the same. The size of amacroblock is fixed in H.263, and therefore does not need to besignaled.

Changes of picture size in predicted pictures became more mainstream inmodern video coding. For example, VP9 allows reference pictureresampling (RPR) and change of resolution for a whole picture.Similarly, certain proposals made towards VVC (including, for example,Hendry, et. al, “On adaptive resolution change (ARC) for VVC”, JointVideo Team document JVET-M0135-v1, Jan. 9-19, 2019, incorporated hereinin its entirety) allow for resampling of whole reference pictures todifferent—higher or lower—resolutions. In that document, differentcandidate resolutions are suggested to be coded in the sequenceparameter set and referred to by per-picture syntax elements in thepicture parameter set.

SUMMARY

To address one or more different technical problems, this disclosuredescribed new syntaxes and use thereof designed for signaling of scalingin a video bitstream. Thus, improved (de)coding efficiency can beachieved.

According to embodiments herein, with Reference Picture Resampling (RPR)or Adaptive Resolution Change (ARC), the additional burden forscalability support is may be achieved by a modification of thehigh-level syntax (HLS). In technical aspects, the inter-layerprediction is employed in a scalable system to improve the codingefficiency of the enhancement layers. In addition to the spatial andtemporal motion-compensated predictions that are available in asingle-layer codec, the inter-layer prediction uses the resampled videodata of the reconstructed reference picture from a reference layer topredict the current enhancement layer. Then, the resampling process forinter-layer prediction is performed at the block-level, by modifying theexisting interpolation process for motion compensation. It means that noadditional resampling process is needed to support scalability. In thisdisclosure, high-level syntax elements to support spatial/qualityscalability using the RPR are disclosed.

There is included a method and apparatus comprising memory configured tostore computer program code and a processor or processors configured toaccess the computer program code and operate as instructed by thecomputer program code. The computer program code includes parsing codeconfigured to cause the at least one processor to parse at least onevideo parameter set (VPS) comprising at least one syntax elementindicating whether at least one layer in the scalable bitstream is oneof a dependent layer of the scalable bitstream and an independent layerof the scalable bitstream, determining code configured to cause the atleast one processor to determine a number of dependent layers, includingthe dependent layer, of the scalable bitstream based on a plurality offlags included in the VPS, first decoding code configured to cause theat least one processor to decode a picture in the dependent layer byparsing and interpreting an inter-layer reference picture (ILRP) list,and second decoding code configured to cause the at least one processorto decode a picture in an independent layer without parsing andinterpreting the ILRP list.

According to embodiments, the second decoding code is further configuredto cause the at least one processor to decode the picture in theindependent layer by parsing and interpreting a reference picture listwhich does not include any decoded picture of another layer.

According to embodiments, the inter-layer reference picture listincludes a decoded picture of the other layer.

According to embodiments, the parsing code is further configured tocause the at least one processor to parse the at least one VPS bydetermining whether another syntax element indicates a maximum number oflayers.

According to embodiments, the parsing code is further configured tocause the at least one processor to parse the at least one VPS bydetermining whether the VPS comprises a flag indicating whether anotherlayer in the scalable bitstream is a reference layer for the at leastone layer.

According to embodiments, the parsing code is further configured tocause the at least one processor to parse the at least one VPS bydetermining whether the flag indicates the other layer as the referencelayer for the at least one layer by specifying an index of the otherlayer and an index of the at least one layer, and the parsing code isfurther configured to cause the at least one processor to parse the atleast one VPS by determining whether the VPS comprises another syntaxelement indicating a value less than the determined number of dependentlayers.

According to embodiments, the parsing code is further configured tocause the at least one processor to parse the at least one VPS bydetermining whether the flag indicates the other layer as not being thereference layer for the at least one layer by specifying an index of theother layer and an index of the at least one layer, and the parsing codeis further configured to cause the at least one processor to parse theat least one VPS by determining whether the VPS comprises another syntaxelement indicating a value less than the determined number of dependentlayers.

According to embodiments, the parsing code is further configured tocause the at least one processor to parse the at least one VPS bydetermining whether the VPS comprises a flag indicating whether aplurality of layers, including the at least one layer, are to be decodedby interpreting the ILRP list.

According to embodiments, the parsing code is further configured tocause the at least one processor to parse the at least one VPS bydetermining whether the VPS comprises a flag indicating whether aplurality of layers, including the at least one layer, are to be decodedwithout interpreting the ILRP list.

According to embodiments, the parsing code is further configured tocause the at least one processor to parse the at least one VPS furthercomprises determining whether the VPS comprises a flag indicatingwhether a plurality of layers, including the at least one layer, are tobe decoded by interpreting the ILRP list.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features, the nature, and various advantages of the disclosedsubject matter will be more apparent from the following detaileddescription and the accompanying drawings in which:

FIG. 1 is a schematic illustration of a simplified block diagram of acommunication system in accordance with embodiment.

FIG. 2 is a schematic illustration of a simplified block diagram of acommunication system in accordance with embodiments.

FIG. 3 is a schematic illustration of a simplified block diagram of adecoder in accordance with embodiments.

FIG. 4 is a schematic illustration of a simplified block diagram of anencoder in accordance with embodiments.

FIG. 5A is a schematic illustration of options for signaling ARC/RPRparameters in accordance with related art.

FIG. 5B is a schematic illustration of options for signaling ARC/RPRparameters in accordance with related art.

FIG. 5C is a schematic illustration of options for signaling ARC/RPRparameters in accordance with embodiments.

FIG. 5D is a schematic illustration of options for signaling ARC/RPRparameters in accordance with embodiments.

FIG. 5E is a schematic illustration of options for signaling ARC/RPRparameters in accordance with embodiments.

FIG. 6 is a schematic illustration of signaling picture resolutions inaccordance with embodiments.

FIG. 7 is a schematic illustration of signaling picture size andconformance window in SPS in accordance with embodiments.

FIG. 8 is a schematic illustration of signaling inter-layer predictionpresence in SPS in accordance with embodiments.

FIG. 9 is a schematic illustration of signaling inter-layer predictionindex in slice header in accordance with embodiments.

FIG. 10 is a schematic illustration of a computer system in accordancewith embodiments.

DETAILED DESCRIPTION

The proposed features discussed below may be used separately or combinedin any order. Further, the embodiments may be implemented by processingcircuitry (e.g., one or more processors or one or more integratedcircuits). In one example, the one or more processors execute a programthat is stored in a non-transitory computer-readable medium.

FIG. 1 illustrates a simplified block diagram of a communication system(100) according to an embodiment of the present disclosure. The system(100) may include at least two terminals (110 and 120) interconnectedvia a network (150). For unidirectional transmission of data, a firstterminal (110) may code video data at a local location for transmissionto the other terminal (120) via the network (150). The second terminal(120) may receive the coded video data of the other terminal from thenetwork (150), decode the coded data and display the recovered videodata. Unidirectional data transmission may be common in media servingapplications and the like.

FIG. 1 illustrates a second pair of terminals (130, 140) provided tosupport bidirectional transmission of coded video that may occur, forexample, during videoconferencing. For bidirectional transmission ofdata, each terminal (130, 140) may code video data captured at a locallocation for transmission to the other terminal via the network (150).Each terminal (130, 140) also may receive the coded video datatransmitted by the other terminal, may decode the coded data and maydisplay the recovered video data at a local display device.

In FIG. 1, the terminals (110, 120, 130, 140) may be illustrated asservers, personal computers and smart phones but the principles of thepresent disclosure may be not so limited. Embodiments of the presentdisclosure find application with laptop computers, tablet computers,media players and/or dedicated video conferencing equipment. The network(150) represents any number of networks that convey coded video dataamong the terminals (110, 120, 130, 140), including for example wirelineand/or wireless communication networks. The communication network (150)may exchange data in circuit-switched and/or packet-switched channels.Representative networks include telecommunications networks, local areanetworks, wide area networks and/or the Internet. For the purposes ofthe present discussion, the architecture and topology of the network(150) may be immaterial to the operation of the present disclosureunless explained herein below.

FIG. 2 illustrates, as an example for an application for the disclosedsubject matter, the placement of a video encoder and decoder in astreaming environment. The disclosed subject matter can be equallyapplicable to other video enabled applications, including, for example,video conferencing, digital TV, storing of compressed video on digitalmedia including CD, DVD, memory stick and the like, and so on.

A streaming system may include a capture subsystem (213), that caninclude a video source (201), for example a digital camera, creating afor example uncompressed video sample stream (202). That sample stream(202), depicted as a bold line to emphasize a high data volume whencompared to encoded video bitstreams, can be processed by an encoder(203) coupled to the camera (201). The encoder (203) can includehardware, software, or a combination thereof to enable or implementaspects of the disclosed subject matter as described in more detailbelow. The encoded video bitstream (204), depicted as a thin line toemphasize the lower data volume when compared to the sample stream, canbe stored on a streaming server (205) for future use. One or morestreaming clients (206, 208) can access the streaming server (205) toretrieve copies (207, 209) of the encoded video bitstream (204). Aclient (206) can include a video decoder (210) which decodes theincoming copy of the encoded video bitstream (207) and creates anoutgoing video sample stream (211) that can be rendered on a display(212) or other rendering device (not depicted). In some streamingsystems, the video bitstreams (204, 207, 209) can be encoded accordingto certain video coding/compression standards. Examples of thosestandards include ITU-T Recommendation H.265. Under development is avideo coding standard informally known as Versatile Video Coding or VVC.The disclosed subject matter may be used in the context of VVC.

FIG. 3 may be a functional block diagram of a video decoder (210)according to an embodiment of the present disclosure.

A receiver (310) may receive one or more codec video sequences to bedecoded by the decoder (210); in the same or another embodiment, onecoded video sequence at a time, where the decoding of each coded videosequence is independent from other coded video sequences. The codedvideo sequence may be received from a channel (312), which may be ahardware/software link to a storage device which stores the encodedvideo data. The receiver (310) may receive the encoded video data withother data, for example, coded audio data and/or ancillary data streams,that may be forwarded to their respective using entities (not depicted).The receiver (310) may separate the coded video sequence from the otherdata. To combat network jitter, a buffer memory (315) may be coupled inbetween receiver (310) and entropy decoder/parser (320) (“parser”henceforth). When receiver (310) is receiving data from a store/forwarddevice of sufficient bandwidth and controllability, or from anisosychronous network, the buffer (315) may not be needed, or can besmall. For use on best effort packet networks such as the Internet, thebuffer (315) may be required, can be comparatively large and canadvantageously of adaptive size.

The video decoder (210) may include an parser (320) to reconstructsymbols (321) from the entropy coded video sequence. Categories of thosesymbols include information used to manage operation of the decoder(210), and potentially information to control a rendering device such asa display (212) that is not an integral part of the decoder but can becoupled to it, as was shown in FIG. 2. The control information for therendering device(s) may be in the form of Supplementary EnhancementInformation (SEI messages) or Video Usability Information (VUI)parameter set fragments (not depicted). The parser (320) mayparse/entropy-decode the coded video sequence received. The coding ofthe coded video sequence can be in accordance with a video codingtechnology or standard, and can follow principles well known to a personskilled in the art, including variable length coding, Huffman coding,arithmetic coding with or without context sensitivity, and so forth. Theparser (320) may extract from the coded video sequence, a set ofsubgroup parameters for at least one of the subgroups of pixels in thevideo decoder, based upon at least one parameters corresponding to thegroup. Subgroups can include Groups of Pictures (GOPs), pictures, tiles,slices, macroblocks, Coding Units (CUs), blocks, Transform Units (TUs),Prediction Units (PUs) and so forth. The entropy decoder/parser may alsoextract from the coded video sequence information such as transformcoefficients, quantizer parameter values, motion vectors, and so forth.

The parser (320) may perform entropy decoding/parsing operation on thevideo sequence received from the buffer (315), so to create symbols(321).

Reconstruction of the symbols (321) can involve multiple different unitsdepending on the type of the coded video picture or parts thereof (suchas: inter and intra picture, inter and intra block), and other factors.Which units are involved, and how, can be controlled by the subgroupcontrol information that was parsed from the coded video sequence by theparser (320). The flow of such subgroup control information between theparser (320) and the multiple units below is not depicted for clarity.

Beyond the functional blocks already mentioned, decoder 210 can beconceptually subdivided into a number of functional units as describedbelow. In a practical implementation operating under commercialconstraints, many of these units interact closely with each other andcan, at least partly, be integrated into each other. However, for thepurpose of describing the disclosed subject matter, the conceptualsubdivision into the functional units below is appropriate.

A first unit is the scaler/inverse transform unit (351). Thescaler/inverse transform unit (351) receives quantized transformcoefficient as well as control information, including which transform touse, block size, quantization factor, quantization scaling matrices,etc. as symbol(s) (321) from the parser (320). It can output blockscomprising sample values, that can be input into aggregator (355).

In some cases, the output samples of the scaler/inverse transform (351)can pertain to an intra coded block; that is: a block that is not usingpredictive information from previously reconstructed pictures, but canuse predictive information from previously reconstructed parts of thecurrent picture. Such predictive information can be provided by an intrapicture prediction unit (352). In some cases, the intra pictureprediction unit (352) generates a block of the same size and shape ofthe block under reconstruction, using surrounding already reconstructedinformation fetched from the current (partly reconstructed) picture(356). The aggregator (355), in some cases, adds, on a per sample basis,the prediction information the intra prediction unit (352) has generatedto the output sample information as provided by the scaler/inversetransform unit (351).

In other cases, the output samples of the scaler/inverse transform unit(351) can pertain to an inter coded, and potentially motion compensatedblock. In such a case, a Motion Compensation Prediction unit (353) canaccess reference picture memory (357) to fetch samples used forprediction. After motion compensating the fetched samples in accordancewith the symbols (321) pertaining to the block, these samples can beadded by the aggregator (355) to the output of the scaler/inversetransform unit (in this case called the residual samples or residualsignal) so to generate output sample information. The addresses withinthe reference picture memory form where the motion compensation unitfetches prediction samples can be controlled by motion vectors,available to the motion compensation unit in the form of symbols (321)that can have, for example X, Y, and reference picture components.Motion compensation also can include interpolation of sample values asfetched from the reference picture memory when sub-sample exact motionvectors are in use, motion vector prediction mechanisms, and so forth.

The output samples of the aggregator (355) can be subject to variousloop filtering techniques in the loop filter unit (356). Videocompression technologies can include in-loop filter technologies thatare controlled by parameters included in the coded video bitstream andmade available to the loop filter unit (356) as symbols (321) from theparser (320), but can also be responsive to meta-information obtainedduring the decoding of previous (in decoding order) parts of the codedpicture or coded video sequence, as well as responsive to previouslyreconstructed and loop-filtered sample values.

The output of the loop filter unit (356) can be a sample stream that canbe output to the render device (212) as well as stored in the referencepicture memory (356) for use in future inter-picture prediction.

Certain coded pictures, once fully reconstructed, can be used asreference pictures for future prediction. Once a coded picture is fullyreconstructed and the coded picture has been identified as a referencepicture (by, for example, parser (320)), the current reference picture(356) can become part of the reference picture buffer (357), and a freshcurrent picture memory can be reallocated before commencing thereconstruction of the following coded picture.

The video decoder 320 may perform decoding operations according to apredetermined video compression technology that may be documented in astandard, such as ITU-T Rec. H.265. The coded video sequence may conformto a syntax specified by the video compression technology or standardbeing used, in the sense that it adheres to the syntax of the videocompression technology or standard, as specified in the videocompression technology document or standard and specifically in theprofiles document therein. Also necessary for compliance can be that thecomplexity of the coded video sequence is within bounds as defined bythe level of the video compression technology or standard. In somecases, levels restrict the maximum picture size, maximum frame rate,maximum reconstruction sample rate (measured in, for example megasamplesper second), maximum reference picture size, and so on. Limits set bylevels can, in some cases, be further restricted through HypotheticalReference Decoder (HRD) specifications and metadata for HRD buffermanagement signaled in the coded video sequence.

In an embodiment, the receiver (310) may receive additional (redundant)data with the encoded video. The additional data may be included as partof the coded video sequence(s). The additional data may be used by thevideo decoder (320) to properly decode the data and/or to moreaccurately reconstruct the original video data. Additional data can bein the form of, for example, temporal, spatial, or SNR enhancementlayers, redundant slices, redundant pictures, forward error correctioncodes, and so on.

FIG. 4 may be a functional block diagram of a video encoder (203)according to an embodiment of the present disclosure.

The encoder (203) may receive video samples from a video source (201)(that is not part of the encoder) that may capture video image(s) to becoded by the encoder (203).

The video source (201) may provide the source video sequence to be codedby the encoder (203) in the form of a digital video sample stream thatcan be of any suitable bit depth (for example: 8 bit, 10 bit, 12 bit, .. . ), any colorspace (for example, BT.601 Y CrCB, RGB, . . . ) and anysuitable sampling structure (for example Y CrCb 4:2:0, Y CrCb 4:4:4). Ina media serving system, the video source (201) may be a storage devicestoring previously prepared video. In a videoconferencing system, thevideo source (203) may be a camera that captures local image informationas a video sequence. Video data may be provided as a plurality ofindividual pictures that impart motion when viewed in sequence. Thepictures themselves may be organized as a spatial array of pixels,wherein each pixel can comprise one or more sample depending on thesampling structure, color space, etc. in use. A person skilled in theart can readily understand the relationship between pixels and samples.The description below focuses on samples.

According to an embodiment, the encoder (203) may code and compress thepictures of the source video sequence into a coded video sequence (443)in real time or under any other time constraints as required by theapplication. Enforcing appropriate coding speed is one function ofController (450). Controller controls other functional units asdescribed below and is functionally coupled to these units. The couplingis not depicted for clarity. Parameters set by controller can includerate control related parameters (picture skip, quantizer, lambda valueof rate-distortion optimization techniques, . . . ), picture size, groupof pictures (GOP) layout, maximum motion vector search range, and soforth. A person skilled in the art can readily identify other functionsof controller (450) as they may pertain to video encoder (203) optimizedfor a certain system design.

Some video encoders operate in what a person skilled in the are readilyrecognizes as a “coding loop”. As an oversimplified description, acoding loop can consist of the encoding part of an encoder (430)(“source coder” henceforth) (responsible for creating symbols based onan input picture to be coded, and a reference picture(s)), and a (local)decoder (433) embedded in the encoder (203) that reconstructs thesymbols to create the sample data a (remote) decoder also would create(as any compression between symbols and coded video bitstream islossless in the video compression technologies considered in thedisclosed subject matter). That reconstructed sample stream is input tothe reference picture memory (434). As the decoding of a symbol streamleads to bit-exact results independent of decoder location (local orremote), the reference picture buffer content is also bit exact betweenlocal encoder and remote encoder. In other words, the prediction part ofan encoder “sees” as reference picture samples exactly the same samplevalues as a decoder would “see” when using prediction during decoding.This fundamental principle of reference picture synchronicity (andresulting drift, if synchronicity cannot be maintained, for examplebecause of channel errors) is well known to a person skilled in the art.

The operation of the “local” decoder (433) can be the same as of a“remote” decoder (210), which has already been described in detail abovein conjunction with FIG. 3. Briefly referring also to FIG. 3, however,as symbols are available and en/decoding of symbols to a coded videosequence by entropy coder (445) and parser (320) can be lossless, theentropy decoding parts of decoder (210), including channel (312),receiver (310), buffer (315), and parser (320) may not be fullyimplemented in local decoder (433).

An observation that can be made at this point is that any decodertechnology except the parsing/entropy decoding that is present in adecoder also necessarily needs to be present, in substantially identicalfunctional form, in a corresponding encoder. For this reason, thedisclosed subject matter focuses on decoder operation. The descriptionof encoder technologies can be abbreviated as they are the inverse ofthe comprehensively described decoder technologies. Only in certainareas a more detail description is required and provided below.

As part of its operation, the source coder (430) may perform motioncompensated predictive coding, which codes an input frame predictivelywith reference to one or more previously-coded frames from the videosequence that were designated as “reference frames.” In this manner, thecoding engine (432) codes differences between pixel blocks of an inputframe and pixel blocks of reference frame(s) that may be selected asprediction reference(s) to the input frame.

The local video decoder (433) may decode coded video data of frames thatmay be designated as reference frames, based on symbols created by thesource coder (430). Operations of the coding engine (432) mayadvantageously be lossy processes. When the coded video data may bedecoded at a video decoder (not shown in FIG. 4), the reconstructedvideo sequence typically may be a replica of the source video sequencewith some errors. The local video decoder (433) replicates decodingprocesses that may be performed by the video decoder on reference framesand may cause reconstructed reference frames to be stored in thereference picture cache (434). In this manner, the encoder (203) maystore copies of reconstructed reference frames locally that have commoncontent as the reconstructed reference frames that will be obtained by afar-end video decoder (absent transmission errors).

The predictor (435) may perform prediction searches for the codingengine (432). That is, for a new frame to be coded, the predictor (435)may search the reference picture memory (434) for sample data (ascandidate reference pixel blocks) or certain metadata such as referencepicture motion vectors, block shapes, and so on, that may serve as anappropriate prediction reference for the new pictures. The predictor(435) may operate on a sample block-by-pixel block basis to findappropriate prediction references. In some cases, as determined bysearch results obtained by the predictor (435), an input picture mayhave prediction references drawn from multiple reference pictures storedin the reference picture memory (434).

The controller (450) may manage coding operations of the video coder(430), including, for example, setting of parameters and subgroupparameters used for encoding the video data.

Output of all aforementioned functional units may be subjected toentropy coding in the entropy coder (445). The entropy coder translatesthe symbols as generated by the various functional units into a codedvideo sequence, by loss-less compressing the symbols according totechnologies known to a person skilled in the art as, for exampleHuffman coding , variable length coding, arithmetic coding, and soforth.

The transmitter (440) may buffer the coded video sequence(s) as createdby the entropy coder (445) to prepare it for transmission via acommunication channel (460), which may be a hardware/software link to astorage device which would store the encoded video data. The transmitter(440) may merge coded video data from the video coder (430) with otherdata to be transmitted, for example, coded audio data and/or ancillarydata streams (sources not shown).

The controller (450) may manage operation of the encoder (203). Duringcoding, the controller (450) may assign to each coded picture a certaincoded picture type, which may affect the coding techniques that may beapplied to the respective picture. For example, pictures often may beassigned as one of the following frame types:

An Intra Picture (I picture) may be one that may be coded and decodedwithout using any other frame in the sequence as a source of prediction.Some video codecs allow for different types of Intra pictures,including, for example Independent Decoder Refresh Pictures. A personskilled in the art is aware of those variants of I pictures and theirrespective applications and features.

A Predictive picture (P picture) may be one that may be coded anddecoded using intra prediction or inter prediction using at most onemotion vector and reference index to predict the sample values of eachblock.

A Bi-directionally Predictive Picture (B Picture) may be one that may becoded and decoded using intra prediction or inter prediction using atmost two motion vectors and reference indices to predict the samplevalues of each block. Similarly, multiple-predictive pictures can usemore than two reference pictures and associated metadata for thereconstruction of a single block.

Source pictures commonly may be subdivided spatially into a plurality ofsample blocks (for example, blocks of 4×4, 8×8, 4×8, or 16×16 sampleseach) and coded on a block-by-block basis. Blocks may be codedpredictively with reference to other (already coded) blocks asdetermined by the coding assignment applied to the blocks' respectivepictures. For example, blocks of I pictures may be codednon-predictively or they may be coded predictively with reference toalready coded blocks of the same picture (spatial prediction or intraprediction). Pixel blocks of P pictures may be coded non-predictively,via spatial prediction or via temporal prediction with reference to onepreviously coded reference pictures. Blocks of B pictures may be codednon-predictively, via spatial prediction or via temporal prediction withreference to one or two previously coded reference pictures.

The video coder (203) may perform coding operations according to apredetermined video coding technology or standard, such as ITU-T Rec.H.265. In its operation, the video coder (203) may perform variouscompression operations, including predictive coding operations thatexploit temporal and spatial redundancies in the input video sequence.The coded video data, therefore, may conform to a syntax specified bythe video coding technology or standard being used.

In an embodiment, the transmitter (440) may transmit additional datawith the encoded video. The video coder (430) may include such data aspart of the coded video sequence. Additional data may comprisetemporal/spatial/SNR enhancement layers, other forms of redundant datasuch as redundant pictures and slices, Supplementary EnhancementInformation (SEI) messages, Visual Usability Information (VUI) parameterset fragments, and so on.

Before describing certain aspects of the disclosed subject matter inmore detail, a few terms need to be introduced that will be referred toin the remainder of this description.

Sub-Picture henceforth refers to an, in some cases, rectangulararrangement of samples, blocks, macroblocks, coding units, or similarentities that are semantically grouped, and that may be independentlycoded in changed resolution. One or more sub-pictures may for a picture.One or more coded sub-pictures may form a coded picture. One or moresub-pictures may be assembled into a picture, and one or more subpictures may be extracted from a picture. In certain environments, oneor more coded sub-pictures may be assembled in the compressed domainwithout transcoding to the sample level into a coded picture, and in thesame or certain other cases, one or more coded sub-pictures may beextracted from a coded picture in the compressed domain.

Reference Picture Resampling (RPR) or Adaptive Resolution Change (ARC)henceforth refers to mechanisms that allow the change of resolution of apicture or sub-picture within a coded video sequence, by the means of,for example, reference picture resampling. RPR/ARC parameters henceforthrefer to the control information required to perform adaptive resolutionchange, that may include, for example, filter parameters, scalingfactors, resolutions of output and/or reference pictures, variouscontrol flags, and so forth.

Above description is focused on coding and decoding a single,semantically independent coded video picture. Before describing theimplication of coding/decoding of multiple sub pictures with independentRPR/ARC parameters and its implied additional complexity, options forsignaling RPR/ARC parameters shall be described.

Referring to FIG. 5, shown are several novel options for signalingRPR/ARC parameters. As noted with each of the options, they have certainadvantages and certain disadvantages from a coding efficiency,complexity, and architecture viewpoint. A video coding standard ortechnology may choose one or more of these options, or options knownfrom previous art, for signaling RPR/ARC parameters. The options may notbe mutually exclusive, and conceivably may be interchanged based onapplication needs, standards technology involved, or encoder's choice.

Classes of RPR/ARC parameters may include:

up/downsample factors, separate or combined in X and Y dimension,

up/downsample factors, with an addition of a temporal dimension,indicating constant speed zoom in/out for a given number of pictures,

any of the above two may involve the coding of one or more presumablyshort syntax elements that may point into a table containing thefactor(s),

resolution, in X or Y dimension, in units of samples, blocks,macroblocks, CUs, or any other suitable granularity, of the inputpicture, output picture, reference picture, coded picture, combined orseparately (If there are more than one resolution (such as, for example,one for input picture, one for reference picture) then, in certaincases, one set of values may be inferred to from another set of values.Such could be gated, for example, by the use of flags. For a moredetailed example, see below.),

“warping” coordinates akin those used in H.263 Annex P, again in asuitable granularity as described above. (H.263 Annex P defines oneefficient way to code such warping coordinates, but other, potentiallymore efficient ways are conceivably also devised. For example, accordingto embodiments the variable length reversible, “Huffman”-style coding ofwarping coordinates of Annex P is replaced by a suitable length binarycoding, where the length of the binary code word could, for example, bederived from a maximum picture size, possibly multiplied by a certainfactor and offset by a certain value, so to allow for “warping” outsideof the maximum picture size's boundaries), and/or

up or downsample filter parameters (In the easiest case, there may beonly a single filter for up and/or downsampling. However, in certaincases, it can be advantageous to allow more flexibility in filterdesign, and that may require to signaling of filter parameters. Suchparameters may be selected through an index in a list of possible filterdesigns, the filter may be fully specified (for example through a listof filter coefficients, using suitable entropy coding techniques), thefilter may be implicitly selected through up/downsample ratios accordingwhich in turn are signaled according to any of the mechanisms mentionedabove, and so forth).

Henceforth, the description assumes the coding of a finite set ofup/downsample factors (the same factor to be used in both X and Ydimension), indicated through a codeword. That codeword canadvantageously be variable length coded, for example using theExt-Golomb code common for certain syntax elements in video codingspecifications such as H.264 and H.265. One suitable mapping of valuesto up/downsample factors can, for example, be according to the followingtable 1:

TABLE 1 Codeword Ext-Golomb Code Original/Target resolution 0 1 1/1 1010 1/1.5 (upscale by 50%)   2 011 1.5/1 (downscale by 50%) 3 00100 1/2(upscale by 100%) 4 00101   2/1 (downscale by 100%)

Many similar mappings could be devised according to the needs of anapplication and the capabilities of the up and downscale mechanismsavailable in a video compression technology or standard. The table couldbe extended to more values. Values may also be represented by entropycoding mechanisms other than Ext-Golomb codes, for example using binarycoding. That may have certain advantages when the resampling factorswere of interest outside the video processing engines (encoder anddecoder foremost) themselves, for example by MANES. It should be notedthat, for the (presumably) most common case where no resolution changeis required, an Ext-Golomb code can be chosen that is short; in thetable above, only a single bit. That can have a coding efficiencyadvantage over using binary codes for the most common case.

The number of entries in the table, as well as their semantics may befully or partially configurable. For example, the basic outline of thetable may be conveyed in a “high” parameter set such as a sequence ordecoder parameter set. Alternatively or in addition, one or more suchtables may be defined in a video coding technology or standard, and maybe selected through for example a decoder or sequence parameter set.

Henceforth, we describe how an upsample/downsample factor (ARCinformation), coded as described above, may be included in a videocoding technology or standard syntax. Similar considerations may applyto one, or a few, codewords controlling up/downsample filters. See belowfor a discussion when comparatively large amounts of data are requiredfor a filter or other data structures.

As shown in the example of FIG. 5A, the illustration (500A) shows thatH.263 Annex P includes the ARC information (502) in the form of fourwarping coordinates into the picture header (501), specifically in theH.263 PLUSPTYPE (503) header extension. This can be a sensible designchoice when a) there is a picture header available, and b) frequentchanges of the ARC information are expected. However, the overhead whenusing H.263-style signaling can be quite high, and scaling factors maynot pertain among picture boundaries as picture header can be oftransient nature. Further, as shown in the example of FIG. 5B, theillustration (500B) shows that JVET-M0135 includes PPS information(504), ARC ref information (505), SPS information (507), and Target ResTable information (506).

According to exemplary embodiments, FIG. 5C illustrates example (500C)in which there is shown tile group header information (508) and ARCinformation (509); FIG. 5D illustrates example (500D) in which there isshown a tile group header information (514), an ARC ref information(513), SPS information (516) and ARC information (515), and FIG. 5Eillustrates example (500E) in which there is shown adaptation parameterset(s) (APS) information (511) and ARC information (512).

FIG. 6 illustrates the table example (600) wherein adaptive resolutionis in use, in this example, coded is an output resolution in units ofsamples (613). The numeral 613 refers to bothoutput_pic_width_in_luma_samples and output_pic_height_in_luma_samples,which together can define the resolution of the output picture.Elsewhere in a video coding technology or standard, certain restrictionsto either value can be defined. For example, a level definition maylimit the number of total output samples, which could be the product ofthe value of those two syntax elements. Also, certain video codingtechnologies or standards, or external technologies or standards suchas, for example, system standards, may limit the numbering range (forexample, one or both dimensions must be divisible by a power of 2number), or the aspect ratio (for example, the width and height must bein a relation such as 4:3 or 16:9). Such restrictions may be introducedto facilitate hardware implementations or for other reasons, as would beunderstood by one of ordinary skill in the art in view of the presentdisclosure.

In certain applications, it can be advisable that the encoder instructsthe decoder to use a certain reference picture size rather thanimplicitly assume that size to be the output picture size. In thisexample, the syntax element reference_pic_size_present_flag (614) gatesthe conditional presence of reference picture dimensions (615) (again,the numeral refers to both width and height).

Certain video coding technologies or standards, for example VP9, supportspatial scalability by implementing certain forms of reference pictureresampling (signaled quite differently from the disclosed subjectmatter) in conjunction with temporal scalability, so to enable spatialscalability. In particular, certain reference pictures may be upsampledusing ARC-style technologies to a higher resolution to form the base ofa spatial enhancement layer. Those upsampled pictures could be refined,using normal prediction mechanisms at the high resolution, so to adddetail.

The disclosed subject matter can be and is used in such an environmentaccording to embodiments. In certain cases, in the same or anotherembodiment, a value in the NAL unit header, for example the Temporal IDfield, can be used to indicate not only the temporal but also thespatial layer. Doing so has certain advantages for certain systemdesigns; for example, existing Selected Forwarding Units (SFU) createdand optimized for temporal layer selected forwarding based on the NALunit header Temporal ID value can be used without modification, forscalable environments. In order to enable that, there may be arequirement for a mapping between the coded picture size and thetemporal layer is indicated by the temporal ID field in the NAL unitheader.

In embodiments, the information on inter-layer dependency may besignaled in VPS (or DPS, SPS, or SEI message). The inter-layerdependency information may be used to identify which layer is used as areference layer to decode the current layer. A decoded picture picA in adirect dependent layer with nuh_layer_id equal to m may be used as areference picture of the picture picB with nuh_layer_id equal to n, whenn is greater than m and two pictures picA and picB belong to the sameaccess unit.

In the same or other embodiments, the inter-layer reference picture(ILRP) list may be explicitly signaled with the inter-predictionreference picture (IPRP) list in a slice header (or a parameter set).Both ILRP lists and IPRP lists may be used for construction of theforward and backward prediction reference picture lists.

In the same or other embodiments, syntax elements in VPS (or otherparameter set) may indicate whether each layer is dependent orindependent. Referring to the example (700) in FIG. 7, the syntaxelement vps_max_layers_minus1 (703) plus 1 may specify the maximumnumber of layers allowed in one or more, potentially all, CVS referringto the VPS (701). vps_all_independent_layers_flag (704) equal to 1 mayspecify that all layers in the CVS are independently coded, i.e. withoutusing inter-layer prediction. vps_all_independent_layers_flag (704)equal to 0 may specify that one or more of the layers in the CVS may useinter-layer prediction. When not present, the value ofvps_all_independent_layers_flag may be inferred to be equal to 1. Whenvps_all_independent_layers_flag is equal to 1, the value ofvps_independent_layer_flag[i] (706) may be inferred to be equal to 1.When vps_all_independent_layers_flag is equal to 0, the value ofvps_independent_layer_flag[0] is inferred to be equal to 1.

Referring to FIG. 7, vps_independent_layer_flag[i] (706) equal to 1 mayspecify that the layer with index i does not use inter-layer prediction.vps_independent_layer_flag[i] equal to 0 may specify that the layer withindex i may use inter-layer prediction and vps_layer_dependency_flag[i]is present in VPS. vps_direct_dependency_flag[i][j] (707) equal to 0 mayspecify that the layer with index j is not a direct reference layer forthe layer with index i. vps_direct_dependency_flag[i][j] equal to 1 mayspecify that the layer with index j is a direct reference layer for thelayer with index i. When vps_direct_dependency_flag[i][j] is not presentfor i and j in the range of 0 to vps_max_layers_minus1, inclusive, itmay be inferred to be equal to 0.

The variable DirectDependentLayerIdx[i][j], specifying the j-th directdependent layer of the i-th layer, and the variableNumDependentLayers[i], specifying the number of dependent layers of thei-th layer, are derived as follows:

for( i = 1; i < vps_max_layers_minus1; i−− ) if(!vps_independent_layer_flag[ i ] ) {  for( j = i, k = 0; j >= 0; j−− )  if( vps_direct_dependency_flag[ i ][ j ] )    DirectDependentLayerIdx[i ][ k++ ] = j   NumDependentLayers[ i ] = k  }

In the same or another embodiment, referring to FIG. 7, whenvps_max_layers_minus1 is greater than zero and the value ofvps_all_independent_layers_flag is equal to zero, vps_output_layers_modeand vps_output_layer_flags[i] may be signaled. vps_output_layers_mode(708) equal to 0 may specify that only the highest layer is output.vps_output_layer_mode equal to 1 specifies that all layers may beoutput. vps_output_layer_mode equal to 2 may specify that the layersthat are output are the layers with vps_output_layer_flag[i] (709) equalto 1. The value of vps_output_layers_mode shall be in the range of 0 to2, inclusive. The value 3 of vps_output_layer_mode may be reserved forfuture use. When not present, the value of vps_output_layers_mode may beinferred to be equal to 1. vps_output_layer_flag[i] equal to 1 mayspecify that the i-th layer is output. vps_output_layer_flag[i] equal to0 may specify that the i-th layer is not output. The listOutputLayerFlag[i], for which the value 1 may specify that the i-thlayer is output and the value 0 specified that the i-th layer is notoutput, is derived as follows:

OutputLayerFlag[ vps_max_layers_minus1 ] = 1 for( i = 0; i <vps_max_layers_minus1; i++ ) if( vps_output_layer_mode = = 0 ) OutputLayerFlag[ i ] = 0 else if( vps_output_layer_mode = = 1 ) OutputLayerFlag[ i ] = 1 else if( vps_output_layer_mode = = 2 ) OutputLayerFlag[ i ] = vps_output_layer_flag[ i ]

In the same or another embodiment, the output of the current picture maybe specified as follows:

-   If PictureOutputFlag is equal to 1 and DpbOutputTime[n] is equal to    CpbRemovalTime[n], the current picture is output.-   Otherwise, if PictureOutputFlag is equal to 0, the current picture    is not output, but will be stored in the DPB as specified in clause.-   Otherwise (PictureOutputFlag is equal to 1 and DpbOutputTime[n] is    greater than CpbRemovalTime[n]), the current picture is output later    and will be stored in the DPB (as specified in clause) and is output    at time DpbOutputTime[n] unless indicated not to be output by the    decoding or inference of no_output_of_prior_pics_flag equal to 1 at    a time that precedes DpbOutputTime[n].    When output, the picture is cropped, using the conformance cropping    window specified in the PPS for the picture.

In the same or another embodiment, PictureOutputFlag may be set asfollows:

-   -   If one of the following conditions is true, PictureOutputFlag is        set equal to 0:        -   the current picture is a RASL picture and            NoIncorrectPicOutputFlag of the associated IRAP picture is            equal to 1.        -   gdr_enabled_flag is equal to 1 and the current picture is a            GDR picture with NoIncorrectPicOutputFlag equal to 1.        -   gdr_enabled_flag is equal to 1, the current picture is            associated with a GDR picture with NoIncorrectPicOutputFlag            equal to 1, and PicOrderCntVal of the current picture is            less than RpPicOrderCntVal of the associated GDR picture.        -   vps_output_layer_mode is equal to 0 or 2 and            OutputLayerFlag[GeneralLayerIdx[nuh_layer_id]] is equal to            0.    -   Otherwise, PictureOutputFlag is set equal to pic_output_flag.

In the same or other embodiments, alternatively, PictureOutputFlag maybe set as follows:

-   -   If one of the following conditions is true, PictureOutputFlag is        set equal to 0:        -   the current picture is a RASL picture and            NoIncorrectPicOutputFlag of the associated IRAP picture is            equal to 1.        -   gdr_enabled_flag is equal to 1 and the current picture is a            GDR picture with NoIncorrectPicOutputFlag equal to 1.        -   gdr_enabled_flag is equal to 1, the current picture is            associated with a GDR picture with NoIncorrectPicOutputFlag            equal to 1, and PicOrderCntVal of the current picture is            less than RpPicOrderCntVal of the associated GDR picture.        -   vps_output_layer_mode is equal to 0 and the current access            unit contains a picture that has PictureOutputFlag equal to            1, has nuh_layer_id nuhLid greater than that of the current            picture, and belongs to an output layer (i.e.,            OutputLayerFlag[GeneralLayerIdx[nuhLid]] is equal to 1).        -   vps_output_layer mode is equal to 2 and            OutputLayerFlag[GeneralLayerIdx[nuh_layer_id]] is equal to            0.    -   Otherwise, PictureOutputFlag is set equal to pic_output_flag.

In the same or other embodiments, a flag in VPS (or another parameterset) may indicate whether ILRP lists are signaled or not for the currentslice (or picture). For example, referring to the example (800) in FIG.8, an inter_layer_ref_pics_present_flag equal to 0 may specify that noILRP is used for inter prediction of any coded picture in the CVS.inter_layer_ref_pics_flag equal to 1 may specify that ILRPs may be usedfor inter prediction of one or more coded pictures in the CVS.

In the same or other embodiments, the inter-layer reference picture(ILRP) list for a picture in the k-th layer may or may not be signaled,when the k-th layer is a dependent layer. However, the ILRP list for apicture in the k-th layer shall not be signaled and any ILRP shall notbe included in the reference picture list, when the k-th layer is anindependent layer.

The value of inter_layer_ref_pics_present_flag may be set equal to 0,when sps_video_parameter_set_id is equal to 0, when nuh_layer_id isequal to 0, or whenvps_independent_layer_flag[GeneralLayerIdx[nuh_layer_id]] is equal to 1.

In the same or other embodiments, referring to the example (900) in FIG.9, a set of syntax elements, which explicitly indicate the ILRP list,may be signaled in SPS, PPS, APS or slice header. The ILRP list may beused to construct the reference picture list of the current picture.

In the same or other embodiments, the ILRP list may be used to identifythe active or inactive reference picture in a decoded picture buffer(DPB). The active reference picture may be used as a reference picturefor decoding the current picture, while the inactive reference picturemay not be used for decoding the current picture, but may be used fordecoding the subsequent picture in decoding order.

In the same or another embodiment, the ILRP list may be used to identifywhich reference picture may be stored in DPB or may be outputted andremoved from DPB. Those information may be used to operate the decoderbased on the hypothetical reference decoder (HRD) model and parameters.

In the same or another embodiment, a syntax elementilrp_idc[listIdx][rplsIdx][i] may be signaled in VPS, SPS, PPS, APS orslice header. The syntax element ilrp_idc[listIdx][rplsIdx][i] specifiesthe index, to the list of directly dependent layers, of the ILRP of i-thentry in ref_pic_list_struct(listIdx, rplsIdx) syntax structure to thelist of directly dependent layers. The value ofilrp_idc[listIdx][rplsIdx][i] shall be in the range of 0 to theGeneralLayerIdx[nuh_layer_id]−1, inclusive.

In the same embodiment, the syntax element ilrp_idc[listIdx][rplsIdx][i]may be an index indicating an ILRP picture among directly dependentlayers, which are identified by vps_direct_dependency_flag[i][j]signaled in VPS. In this case, the value ofilrp_idc[listIdx][rplsIdx][i] shall be in the range of 0 to theNumDependentLayers[GeneralLayerIdx[nuh_layer_id]]−1, inclusive.

In the same embodiment, when the nuh_layer_id of the current layer isequal to k, it may be bit-efficient to signal an index indicating anILRP among directly dependent layers, compared to signaling an indexindicating an ILRP among all layers with nuh_layer_id smaller than k.

In the same or another embodiment, still referring to FIG. 9, thereference picture lists RefPicList[0] and RefPicList[1] may beconstructed as follows:

for( i = 0; i < 2; i++ ) {   for( j = 0, k = 0, pocBase =PicOrderCntVal; j < num_ref_entries[   i ][ RplsIdx[ i ] ]; j++) {   if(!(inter_layer_ref_pic_flag[ i ][ RplsIdx[ i ] ][ j ] && GeneralLayerIdx[nuh_layer_id ]) )  {     if( st_ref_pic_flag[ i ][ RplsIdx[ i ] ][ j ] ){      RefPicPocList[ i ][ j ] = pocBase − DeltaPocValSt[      i ][RplsIdx[ i ] ][ j ]      if( there is a reference picture picA in theDPB with the same      nuh_layer_id as the current picture         andPicOrderCntVal equal to RefPicPocList[ i ][ j ] )       RefPicList[ i ][j ] = picA      else       RefPicList[ i ][ j ] = “no referencepicture”   (−)      pocBase = RefPicPocList[ i ][ j ]     } else {     if( !delta_poc_msb_cycle_lt[ i ][ k ] ) {       if( there is areference picA in the DPB with the same       nuh_layer_id as thecurrent picture and          PicOrderCntVal & ( MaxPicOrderCntLsb −         1 ) equal to PocLsbLt[ i ][ k ] )        RefPicList[ i ][ j ] =picA       else        RefPicList[ i ][ j ] = “no reference picture”      RefPicLtPocList[ i ][ j ] = PocLsbLt[ i ][ k ]      } else {      if( there is a reference picA in the DPB with the same      nuh_layer_id as the current picture and          PicOrderCntValequal to FullPocLt[ i ][ k ] )        RefPicList[ i ][ j ] = picA      else        RefPicList[ i ][ j ] = “no reference picture”      RefPicLtPocList[ i ][ j ] = FullPocLt[ i ][ k ]      }      k++    }    } else {     layerIdx = DirectDependentLayerIdx[GeneralLayerIdx[ nuh_layer_id ] ][ ilrp_idc[ i ][ RplsIdx[ i ] ][ j ] ]    refPicLayerId = vps_layer_id[ layerIdx ]     if( there is areference picture picA in the DPB with     nuh_layer_id equal torefPicLayerId and        the same PicOrderCntVal as the current picture)      RefPicList[ i ][ j ] = picA     else      RefPicList[ i ][ j ] =“no reference picture”    }  } }

The techniques for signaling adaptive resolution parameters describedabove, can be implemented as computer software using computer-readableinstructions and physically stored in one or more computer-readablemedia. For example, FIG. 10 shows a computer system (1000) suitable forimplementing certain embodiments of the disclosed subject matter.

The computer software can be coded using any suitable machine code orcomputer language, that may be subject to assembly, compilation,linking, or like mechanisms to create code comprising instructions thatcan be executed directly, or through interpretation, micro-codeexecution, and the like, by computer central processing units (CPUs),Graphics Processing Units (GPUs), and the like.

The instructions can be executed on various types of computers orcomponents thereof, including, for example, personal computers, tabletcomputers, servers, smartphones, gaming devices, internet of thingsdevices, and the like.

The components shown in FIG. 10 for computer system (1000) are exemplaryin nature and are not intended to suggest any limitation as to the scopeof use or functionality of the computer software implementingembodiments of the present disclosure. Neither should the configurationof components be interpreted as having any dependency or requirementrelating to any one or combination of components illustrated in theexemplary embodiment of a computer system (1000).

Computer system (1000) may include certain human interface inputdevices. Such a human interface input device may be responsive to inputby one or more human users through, for example, tactile input (such as:keystrokes, swipes, data glove movements), audio input (such as: voice,clapping), visual input (such as: gestures), olfactory input (notdepicted). The human interface devices can also be used to capturecertain media not necessarily directly related to conscious input by ahuman, such as audio (such as: speech, music, ambient sound), images(such as: scanned images, photographic images obtain from a still imagecamera), video (such as two-dimensional video, three-dimensional videoincluding stereoscopic video).

Input human interface devices may include one or more of (only one ofeach depicted): keyboard (1001), mouse (1002), trackpad (1003), touchscreen (1010), joystick (1005), microphone (1006), scanner (1007),camera (1008).

Computer system (1000) may also include certain human interface outputdevices. Such human interface output devices may be stimulating thesenses of one or more human users through, for example, tactile output,sound, light, and smell/taste. Such human interface output devices mayinclude tactile output devices (for example tactile feedback by thetouch-screen (1010), or joystick (1005), but there can also be tactilefeedback devices that do not serve as input devices), audio outputdevices (such as: speakers (1009), headphones (not depicted)), visualoutput devices (such as screens (1010) to include CRT screens, LCDscreens, plasma screens, OLED screens, each with or without touch-screeninput capability, each with or without tactile feedback capability—someof which may be capable to output two dimensional visual output or morethan three dimensional output through means such as stereographicoutput; virtual-reality glasses (not depicted), holographic displays andsmoke tanks (not depicted)), and printers (not depicted).

Computer system (1000) can also include human accessible storage devicesand their associated media such as optical media including CD/DVD ROM/RW(1020) with CD/DVD or the like media (1021), thumb-drive (1022),removable hard drive or solid state drive (1023), legacy magnetic mediasuch as tape and floppy disc (not depicted), specialized ROM/ASIC/PLDbased devices such as security dongles (not depicted), and the like.

Those skilled in the art should also understand that term “computerreadable media” as used in connection with the presently disclosedsubject matter does not encompass transmission media, carrier waves, orother transitory signals.

Computer system (1000) can also include interface to one or morecommunication networks. Networks can for example be wireless, wireline,optical. Networks can further be local, wide-area, metropolitan,vehicular and industrial, real-time, delay-tolerant, and so on. Examplesof networks include local area networks such as Ethernet, wireless LANs,cellular networks to include GSM, 3G, 4G, 5G, LTE and the like, TVwireline or wireless wide area digital networks to include cable TV,satellite TV, and terrestrial broadcast TV, vehicular and industrial toinclude CANBus, and so forth. Certain networks commonly require externalnetwork interface adapters that attached to certain general purpose dataports or peripheral buses (1049) (such as, for example USB ports of thecomputer system (1000); others are commonly integrated into the core ofthe computer system (1000) by attachment to a system bus as describedbelow (for example Ethernet interface into a PC computer system orcellular network interface into a smartphone computer system). Using anyof these networks, computer system (1000) can communicate with otherentities. Such communication can be uni-directional, receive only (forexample, broadcast TV), uni-directional send-only (for example CANbus tocertain CANbus devices), or bi-directional, for example to othercomputer systems using local or wide area digital networks. Certainprotocols and protocol stacks can be used on each of those networks andnetwork interfaces as described above.

Aforementioned human interface devices, human-accessible storagedevices, and network interfaces can be attached to a core (1040) of thecomputer system (1000).

The core (1040) can include one or more Central Processing Units (CPU)(1041), Graphics Processing Units (GPU) (1042), specialized programmableprocessing units in the form of Field Programmable Gate Areas (FPGA)(1043), hardware accelerators for certain tasks (1044), and so forth.These devices, along with Read-only memory (ROM) (1045), Random-accessmemory (1046), internal mass storage such as internal non-useraccessible hard drives, SSDs, and the like (1047), may be connectedthrough a system bus (1048). In some computer systems, the system bus(1048) can be accessible in the form of one or more physical plugs toenable extensions by additional CPUs, GPU, and the like. The peripheraldevices can be attached either directly to the core's system bus (1048),or through a peripheral bus (1049). Architectures for a peripheral businclude PCI, USB, and the like.

CPUs (1041), GPUs (1042), FPGAs (1043), and accelerators (1044) canexecute certain instructions that, in combination, can make up theaforementioned computer code. That computer code can be stored in ROM(1045) or RAM (1046). Transitional data can be also be stored in RAM(1046), whereas permanent data can be stored for example, in theinternal mass storage (1047). Fast storage and retrieve to any of thememory devices can be enabled through the use of cache memory, that canbe closely associated with one or more CPU (1041), GPU (1042), massstorage (1047), ROM (1045), RAM (1046), and the like.

The computer readable media can have computer code thereon forperforming various computer-implemented operations. The media andcomputer code can be those specially designed and constructed for thepurposes of the present disclosure, or they can be of the kind wellknown and available to those having skill in the computer software arts.

As an example and not by way of limitation, the computer system havingarchitecture (1000), and specifically the core (1040) can providefunctionality as a result of processor(s) (including CPUs, GPUs, FPGA,accelerators, and the like) executing software embodied in one or moretangible, computer-readable media. Such computer-readable media can bemedia associated with user-accessible mass storage as introduced above,as well as certain storage of the core (1040) that are of non-transitorynature, such as core-internal mass storage (1047) or ROM (1045). Thesoftware implementing various embodiments of the present disclosure canbe stored in such devices and executed by core (1040). Acomputer-readable medium can include one or more memory devices orchips, according to particular needs. The software can cause the core(1040) and specifically the processors therein (including CPU, GPU,FPGA, and the like) to execute particular processes or particular partsof particular processes described herein, including defining datastructures stored in RAM (1046) and modifying such data structuresaccording to the processes defined by the software. In addition or as analternative, the computer system can provide functionality as a resultof logic hardwired or otherwise embodied in a circuit (for example:accelerator (1044)), which can operate in place of or together withsoftware to execute particular processes or particular parts ofparticular processes described herein. Reference to software canencompass logic, and vice versa, where appropriate. Reference to acomputer-readable media can encompass a circuit (such as an integratedcircuit (IC)) storing software for execution, a circuit embodying logicfor execution, or both, where appropriate. The present disclosureencompasses any suitable combination of hardware and software.

While this disclosure has described several exemplary embodiments, thereare alterations, permutations, and various substitute equivalents, whichfall within the scope of the disclosure. It will thus be appreciatedthat those skilled in the art will be able to devise numerous systemsand methods which, although not explicitly shown or described herein,embody the principles of the disclosure and are thus within the spiritand scope thereof.

What is claimed is:
 1. A method for video coding performed by at leastone processor, the method comprising: parsing at least one videoparameter set (VPS) comprising at least one syntax element indicating atleast one of a dependent layer of a scalable bitstream and anindependent layer of the scalable bitstream; decoding a picture in thedependent layer based on parsing and interpreting an inter-layerreference picture (ILRP) list; and decoding a picture in an independentlayer and another picture in the dependent layer each without parsingand interpreting the ILRP list.
 2. The method of claim 1, whereindecoding the picture in the independent layer comprises parsing andinterpreting a reference picture list which does not include any decodedpicture of another layer.
 3. The method of claim 1, wherein theinter-layer reference picture list includes a decoded picture of another layer.
 4. The method of claim 1, wherein parsing the at least oneVPS further comprises determining whether another syntax elementindicates a maximum number of layers.
 5. The method of claim 1, whereinparsing the at least one VPS further comprises determining whether theVPS comprises a flag indicating whether another layer in the scalablebitstream is a reference layer for at least one layer.
 6. The method ofclaim 5, wherein parsing the at least one VPS further comprisesdetermining whether the flag indicates an other layer as the referencelayer for the at least one layer by specifying an index of the otherlayer and an index of the at least one layer, and wherein parsing the atleast one VPS further comprises determining whether the VPS comprisesanother syntax element indicating a value less than the determinednumber of dependent layers.
 7. The method of claim 5, wherein parsingthe at least one VPS further comprises determining whether the flagindicates the other layer as not being the reference layer for the atleast one layer by specifying an index of the other layer and an indexof the at least one layer, and wherein parsing the at least one VPSfurther comprises determining whether the VPS comprises another syntaxelement indicating a value less than the determined number of dependentlayers.
 8. The method of claim 1, wherein parsing the at least one VPSfurther comprises determining whether the VPS comprises a flagindicating whether a plurality of layers, including at least one layer,are to be decoded by interpreting the ILRP list.
 9. The method of claim1, wherein parsing the at least one VPS further comprises determiningwhether the VPS comprises a flag indicating whether a plurality oflayers, including at least one layer, are to be decoded withoutinterpreting the ILRP list.
 10. The method of claim 1, wherein the ILRPlist is signaled with an inter-prediction reference picture (IPRP) listin the VPS.
 11. An apparatus for video coding, the apparatus comprising:at least one memory configured to store computer program code; at leastone processor configured to access the computer program code and operateas instructed by the computer program code, the computer program codeincluding: parsing code configured to cause the at least one processorto parse at least one video parameter set (VPS) comprising at least onesyntax element indicating at least one of a dependent layer of ascalable bitstream and an independent layer of the scalable bitstream;first decoding code configured to cause the at least one processor todecode a picture in the dependent layer based on parsing andinterpreting an inter-layer reference picture (ILRP) list; and seconddecoding code configured to cause the at least one processor to decode apicture in an independent layer and another picture in the dependentlayer each without parsing and interpreting the ILRP list.
 12. Theapparatus of claim 11, wherein the second decoding code is furtherconfigured to cause the at least one processor to decode the picture inthe independent layer by parsing and interpreting a reference picturelist which does not include any decoded picture of another layer. 13.The apparatus of claim 11, wherein the inter-layer reference picturelist includes a decoded picture of an other layer.
 14. The apparatus ofclaim 11, wherein the parsing code is further configured to cause the atleast one processor to parse the at least one VPS by determining whetheranother syntax element indicates a maximum number of layers.
 15. Theapparatus of claim 11, wherein the parsing code is further configured tocause the at least one processor to parse the at least one VPS bydetermining whether the VPS comprises a flag indicating whether anotherlayer in the scalable bitstream is a reference layer for at least onelayer.
 16. The apparatus of claim 15, wherein the parsing code isfurther configured to cause the at least one processor to parse the atleast one VPS by determining whether the flag indicates an other layeras the reference layer for the at least one layer by specifying an indexof the other layer and an index of the at least one layer, and whereinthe parsing code is further configured to cause the at least oneprocessor to parse the at least one VPS by determining whether the VPScomprises another syntax element indicating a value less than thedetermined number of dependent layers.
 17. The apparatus of claim 15,wherein the parsing code is further configured to cause the at least oneprocessor to parse the at least one VPS by determining whether the flagindicates the other layer as not being the reference layer for the atleast one layer by specifying an index of the other layer and an indexof the at least one layer, and wherein the parsing code is furtherconfigured to cause the at least one processor to parse the at least oneVPS by determining whether the VPS comprises another syntax elementindicating a value less than the determined number of dependent layers.18. The apparatus of claim 11, wherein the parsing code is furtherconfigured to cause the at least one processor to parse the at least oneVPS by determining whether the VPS comprises a flag indicating whether aplurality of layers, including at least one layer, are to be decoded byinterpreting the ILRP list.
 19. The apparatus of claim 11, wherein theparsing code is further configured to cause the at least one processorto parse the at least one VPS by determining whether the VPS comprises aflag indicating whether a plurality of layers, including at least onelayer, are to be decoded without interpreting the ILRP list.
 20. Anon-transitory computer readable medium storing a program configured tocause a computer to: parse at least one video parameter set (VPS)comprising at least one syntax element indicating at least one of adependent layer of a scalable bitstream and an independent layer of thescalable bitstream; decode a picture in the dependent layer based onparsing and interpreting an inter-layer reference picture (ILRP) list;and decode a picture in an independent layer and another picture in thedependent layer each without parsing and interpreting the ILRP list.